Hydraulic pulse jet: Test of characteristics and field applications in ultra-deep wells

•HPJ drilling can increase the ROP by installing a HPJ generator before the bit.•Dependent amplitude and frequency of pressure fluctuation of HPJ help break rocks.•Field applications have proven the significant ROP improvement in ultra-deep wells.

Low rate of penetration has been recognized as a major problem affecting the cost of operation in drilling ultra-deep wells (UDW) in the oil and gas industry. This study investigated hydraulic pulse jet (HPJ) technique for increasing rate of penetration in UDW drilling. Results of full-scale testing, numerical simulation, and field applications in the UDW conditions are presented in this paper. The full-scale testing indicates that the HPJ has characteristics of fluid-flow rate dependent amplitude and frequency of pressure fluctuation. This performance was confirmed by numerical simulation of fluid mechanics inside the tool. Field applications in the Tarim and Tahe oilfields, China, show that the rate of penetration (ROP) was increased by 22.2%–54.9% in drilling well sections ended at up to 6162 m. It has been concluded that the HPJ technique is suitable to drilling ultra-deep wells in China.